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		<h1 id="0028-menus-iii---checkmenuitems">0028: Menus III - CheckMenuItems</h1>

<p>Today we’ll cover another type of <code class="language-plaintext highlighter-rouge">MenuItem</code>, the <code class="language-plaintext highlighter-rouge">CheckMenuItem</code>. This post is longer than usual because after doing the simple version, I wanted to do a multiple <code class="language-plaintext highlighter-rouge">CheckMenuItem</code> version as well and that led to a whole can of worms dumped on my desktop. Anyway, let’s get on with it…</p>

<h2 id="single-checkmenuitem">Single CheckMenuItem</h2>

<div class="screenshot-frame">
	<div class="frame-header">
		Results of this example:
	</div>
	<div class="frame-screenshot">
		<figure>
			<img id="img0" src="../images/screenshots/012_menus/menu_09.png" alt="Current example output" />		<!-- img# -->
			
			<!-- Modal for screenshot -->
			<div id="modal0" class="modal">																	<!-- modal# -->
				<span class="close0">&times;</span>															<!-- close# -->
				<img class="modal-content" id="img00" />															<!-- img## -->
				<div id="caption"></div>
			</div>
			
			<script>
			// Get the modal
			var modal = document.getElementById("modal0");														// modal#
			
			// Get the image and insert it inside the modal - use its "alt" text as a caption
			var img = document.getElementById("img0");															// img#
			var modalImg = document.getElementById("img00");													// img##
			var captionText = document.getElementById("caption");

			img.onclick = function()
			{
			  modal.style.display = "block";
			  modalImg.src = this.src;
			  captionText.innerHTML = this.alt;
			}
			
			// Get the <span> element that closes the modal
			var span = document.getElementsByClassName("close0")[0];											// close#
			
			// When the user clicks on <span> (x), close the modal
			span.onclick = function()
			{ 
				modal.style.display = "none";
			}
			</script>
			<figcaption>
			Current example output
			</figcaption>
		</figure>
	</div>

	<div class="frame-terminal">
		<figure class="right">
			<img id="img1" src="../images/screenshots/012_menus/menu_09_term.png" alt="Current example terminal output" />		<!-- img#, filename -->

			<!-- Modal for terminal shot -->
			<div id="modal1" class="modal">																				<!-- modal# -->
				<span class="close1">&times;</span>																		<!-- close# -->
				<img class="modal-content" id="img11" />																		<!-- img## -->
				<div id="caption"></div>
			</div>
			
			<script>
			// Get the modal
			var modal = document.getElementById("modal1");																	// modal#
			
			// Get the image and insert it inside the modal - use its "alt" text as a caption
			var img = document.getElementById("img1");																		// img#
			var modalImg = document.getElementById("img11");																// img##
			var captionText = document.getElementById("caption");

			img.onclick = function()
			{
			  modal.style.display = "block";
			  modalImg.src = this.src;
			  captionText.innerHTML = this.alt;
			}
			
			// Get the <span> element that closes the modal
			var span = document.getElementsByClassName("close1")[0];														// close#
			
			// When the user clicks on <span> (x), close the modal
			span.onclick = function()
			{ 
				modal.style.display = "none";
			}
			</script>

			<figcaption>
				Current example terminal output (click for enlarged view)
			</figcaption>
		</figure>
	</div>

	<div class="frame-footer">																								<!-- ------------- filename (below) --------- -->
		The code file for this example is available <a href="https://github.com/rontarrant/gtkd_demos/blob/master/012_menus/menu_09_single_checkmenuitem.d" target="_blank">here</a>.
	</div>
</div>

<p>For the most part, this is very much the same as other <code class="language-plaintext highlighter-rouge">MenuItem</code>s. It’s created by calling for a new <code class="language-plaintext highlighter-rouge">CheckMenuItem</code> and it’s appended to a <code class="language-plaintext highlighter-rouge">Menu</code> in the same way, but where it strays from the norm is:</p>

<ul>
  <li>you need to decide the default state of the <code class="language-plaintext highlighter-rouge">CheckBox</code>, is it checked or not, and</li>
  <li>the callback needs to handle both checked and unchecked states because it’s triggered by toggling the <code class="language-plaintext highlighter-rouge">CheckBox</code> and *not *just by setting it to an active state.</li>
</ul>

<p>The beauty of this last point is that we can set up the callback to perform two different actions, one when the <code class="language-plaintext highlighter-rouge">CheckBox</code> is activated, another when it’s deactivated. (A similar behaviour is inherited by the <code class="language-plaintext highlighter-rouge">RadioMenuItem</code> as we’ll see in the next blog post.)</p>

<p>The simplest way to write the callback is to check the state of the <code class="language-plaintext highlighter-rouge">CheckBox</code> with <code class="language-plaintext highlighter-rouge">getActive()</code> and decide what to do from there:</p>

<div class="language-d highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="kt">void</span> <span class="n">choose</span><span class="p">(</span><span class="n">CheckMenuItem</span> <span class="n">mi</span><span class="p">)</span>
<span class="p">{</span>
	<span class="k">if</span><span class="p">(</span><span class="n">getActive</span><span class="p">()</span> <span class="p">==</span> <span class="kc">true</span><span class="p">)</span>
	<span class="p">{</span>
		<span class="n">keepItFancy</span><span class="p">();</span>
	<span class="p">}</span>
	<span class="k">else</span>
	<span class="p">{</span>
		<span class="n">makeItPlain</span><span class="p">();</span>
	<span class="p">}</span>
	
<span class="p">}</span> <span class="c1">// choose()</span>
</code></pre></div></div>

<p>While digging into this widget, I found myself unable to resist doing a more complex version with multiple <code class="language-plaintext highlighter-rouge">CheckMenuItem</code>s, so here we go…</p>

<h2 id="multiple-checkmenuitems-and-tracking-their-states">Multiple CheckMenuItems and Tracking Their States</h2>

<div class="screenshot-frame">
	<div class="frame-header">
		Results of this example:
	</div>
	<div class="frame-screenshot">
		<figure>
			<img id="img2" src="../images/screenshots/012_menus/menu_10.png" alt="Current example output" />		<!-- img# -->
			
			<!-- Modal for screenshot -->
			<div id="modal2" class="modal">																<!-- modal# -->
				<span class="close2">&times;</span>														<!-- close# -->
				<img class="modal-content" id="img22" />														<!-- img## -->
				<div id="caption"></div>
			</div>
			
			<script>
			// Get the modal
			var modal = document.getElementById("modal2");													// modal#
			
			// Get the image and insert it inside the modal - use its "alt" text as a caption
			var img = document.getElementById("img2");														// img#
			var modalImg = document.getElementById("img22");												// img##
			var captionText = document.getElementById("caption");

			img.onclick = function()
			{
			  modal.style.display = "block";
			  modalImg.src = this.src;
			  captionText.innerHTML = this.alt;
			}
			
			// Get the <span> element that closes the modal
			var span = document.getElementsByClassName("close2")[0];										// close#
			
			// When the user clicks on <span> (x), close the modal
			span.onclick = function()
			{ 
				modal.style.display = "none";
			}
			</script>
			<figcaption>
			Current example output
			</figcaption>
		</figure>
	</div>

	<div class="frame-terminal">
		<figure class="right">
			<img id="img3" src="../images/screenshots/012_menus/menu_10_term.png" alt="Current example terminal output" /> 		<!-- img#, filename -->

			<!-- Modal for terminal shot -->
			<div id="modal3" class="modal">																			<!-- modal# -->
				<span class="close3">&times;</span>																	<!-- close# -->
				<img class="modal-content" id="img33" />																	<!-- img## -->
				<div id="caption"></div>
			</div>
			
			<script>
			// Get the modal
			var modal = document.getElementById("modal3");																// modal#
			
			// Get the image and insert it inside the modal - use its "alt" text as a caption
			var img = document.getElementById("img3");																	// img#
			var modalImg = document.getElementById("img33");															// img##
			var captionText = document.getElementById("caption");

			img.onclick = function()
			{
			  modal.style.display = "block";
			  modalImg.src = this.src;
			  captionText.innerHTML = this.alt;
			}
			
			// Get the <span> element that closes the modal
			var span = document.getElementsByClassName("close3")[0];													// close#
			
			// When the user clicks on <span> (x), close the modal
			span.onclick = function()
			{ 
				modal.style.display = "none";
			}
			</script>

			<figcaption>
				Current example terminal output (click for enlarged view)
			</figcaption>
		</figure>
	</div>

	<div class="frame-footer">																							<!--------- filename (below) ------------>
		The code file for this example is available <a href="https://github.com/rontarrant/gtkd_demos/blob/master/012_menus/menu_10_multiple_checkmenuitems.d" target="_blank">here</a>.
	</div>
</div>

<p>Before we look at the <code class="language-plaintext highlighter-rouge">CheckMenuItem</code>s themselves…</p>

<h3 id="the-observedfeatureslist-object">The ObservedFeaturesList Object</h3>

<p>This example spotlights an imaginary object and the features controlled with the <code class="language-plaintext highlighter-rouge">CheckMenuItem</code>s. Here’s the code to define this imaginary object:</p>

<div class="language-d highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="k">class</span> <span class="n">ObservedFeaturesList</span>
<span class="p">{</span>
	<span class="kt">bool</span><span class="p">[</span><span class="nb">string</span><span class="p">]</span> <span class="n">features</span><span class="p">;</span>

	<span class="k">this</span><span class="p">()</span>
	<span class="p">{</span>
		<span class="n">features</span> <span class="p">=</span> <span class="p">[</span><span class="s">"Fancy"</span> <span class="p">:</span> <span class="kc">true</span><span class="p">,</span> <span class="s">"Fortified"</span> <span class="p">:</span> <span class="kc">false</span><span class="p">,</span> <span class="s">"Extra Large"</span> <span class="p">:</span> <span class="kc">false</span><span class="p">,</span> <span class="s">"Soft &amp; Fluffy"</span> <span class="p">:</span> <span class="kc">true</span><span class="p">];</span>
		
	<span class="p">}</span> <span class="c1">// this()</span>
	
	
	<span class="kt">void</span> <span class="n">setFeature</span><span class="p">(</span><span class="nb">string</span> <span class="n">featureName</span><span class="p">,</span> <span class="kt">bool</span> <span class="n">state</span><span class="p">)</span>
	<span class="p">{</span>
		<span class="n">features</span><span class="p">[</span><span class="n">featureName</span><span class="p">]</span> <span class="p">=</span> <span class="n">state</span><span class="p">;</span>
		
	<span class="p">}</span> <span class="c1">// setFeature()</span>
	
	
	<span class="kt">bool</span> <span class="n">getFeature</span><span class="p">(</span><span class="nb">string</span> <span class="n">featureName</span><span class="p">)</span>
	<span class="p">{</span>
		<span class="k">return</span><span class="p">(</span><span class="n">features</span><span class="p">[</span><span class="n">featureName</span><span class="p">]);</span>
		
	<span class="p">}</span> <span class="c1">// getFeature()</span>
	
	
	<span class="kt">void</span> <span class="n">listFeatures</span><span class="p">()</span>
	<span class="p">{</span>
		<span class="k">foreach</span><span class="p">(</span><span class="n">name</span><span class="p">,</span> <span class="n">feature</span><span class="p">;</span> <span class="n">features</span><span class="p">)</span>
		<span class="p">{</span>
			<span class="n">writeln</span><span class="p">(</span><span class="n">name</span><span class="p">,</span> <span class="s">" = "</span><span class="p">,</span> <span class="n">feature</span><span class="p">);</span>
		<span class="p">}</span>
		
	<span class="p">}</span> <span class="c1">// listFeatures()</span>
	
<span class="p">}</span> <span class="c1">// class ObservedFeaturesList</span>
</code></pre></div></div>

<p>This is a different approach than we’ve taken before. This class keeps track of:</p>

<ul>
  <li>the number of features,</li>
  <li>their names, and</li>
  <li>their states (on or off, signified by true or false)</li>
</ul>

<p>The <code class="language-plaintext highlighter-rouge">features</code> associative array is the only part of the code we need to fiddle with when deciding which features are turned on by default, another reason why using a generic approach to coding other classes makes sense.</p>

<p>Also, the key names are used as labels when creating the <code class="language-plaintext highlighter-rouge">CheckMenuItem</code>s, so there’s another thing we only have to deal with here in this one place.</p>

<p>This <code class="language-plaintext highlighter-rouge">ObservedFeaturesList</code> object is instantiated in…</p>

<h2 id="back-to-the-top">Back to the Top</h2>

<p>Jumping back to the <code class="language-plaintext highlighter-rouge">TextRigWindow</code> class, we see some changes to our usual code:</p>

<div class="language-d highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="k">class</span> <span class="n">TestRigWindow</span> <span class="p">:</span> <span class="n">MainWindow</span>
<span class="p">{</span>
	<span class="nb">string</span> <span class="n">title</span> <span class="p">=</span> <span class="s">"CheckMenuItem Example"</span><span class="p">;</span>
	<span class="n">ObservedFeaturesList</span> <span class="n">observedList</span><span class="p">;</span>

	<span class="k">this</span><span class="p">()</span>
	<span class="p">{</span>
		<span class="k">super</span><span class="p">(</span><span class="n">title</span><span class="p">);</span>
		<span class="n">setDefaultSize</span><span class="p">(</span><span class="mi">640</span><span class="p">,</span> <span class="mi">480</span><span class="p">);</span>
		<span class="n">addOnDestroy</span><span class="p">(&amp;</span><span class="n">quitApp</span><span class="p">);</span>

		<span class="n">observedList</span> <span class="p">=</span> <span class="k">new</span> <span class="n">ObservedFeaturesList</span><span class="p">();</span>
		
		<span class="n">AppBox</span> <span class="n">appBox</span> <span class="p">=</span> <span class="k">new</span> <span class="n">AppBox</span><span class="p">(</span><span class="n">observedList</span><span class="p">);</span>
		<span class="n">add</span><span class="p">(</span><span class="n">appBox</span><span class="p">);</span>
		
		<span class="n">showAll</span><span class="p">();</span>
		
	<span class="p">}</span> <span class="c1">// this()</span>
	
	
	<span class="kt">void</span> <span class="n">quitApp</span><span class="p">(</span><span class="n">Widget</span> <span class="n">w</span><span class="p">)</span>
	<span class="p">{</span>
		<span class="n">observedList</span><span class="p">.</span><span class="n">listFeatures</span><span class="p">();</span>
		
		<span class="n">Main</span><span class="p">.</span><span class="n">quit</span><span class="p">();</span>
		
	<span class="p">}</span> <span class="c1">// quitApp()</span>
	
<span class="p">}</span> <span class="c1">// TestRigWindow</span>
</code></pre></div></div>

<p>Because all of the <code class="language-plaintext highlighter-rouge">CheckMenuItem</code>s need access to the <code class="language-plaintext highlighter-rouge">ObservedFeaturesList</code> and I also wanted to duplicate <code class="language-plaintext highlighter-rouge">Exit</code> <code class="language-plaintext highlighter-rouge">MenuItem</code> action when the user clicks the window’s <em>Close</em> button, I created the observed object here and passed it down through the hierarchy.</p>

<h2 id="the-filemenu-class">The FileMenu Class</h2>

<p>Here, because the <code class="language-plaintext highlighter-rouge">CheckMenuItem</code>s are all so similar, we can get away grabbing the names (<code class="language-plaintext highlighter-rouge">itemKey</code>) from within a <code class="language-plaintext highlighter-rouge">foreach</code> loop to create the items:</p>

<div class="language-d highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="k">class</span> <span class="n">FileMenu</span> <span class="p">:</span> <span class="n">Menu</span>
<span class="p">{</span>
	<span class="n">FeatureCheckMenuItem</span><span class="p">[]</span> <span class="n">featureItemArray</span><span class="p">;</span>
	<span class="n">FeatureCheckMenuItem</span> <span class="n">featureItem</span><span class="p">;</span>
	<span class="n">ExitItem</span> <span class="n">exitItem</span><span class="p">;</span>
	
	<span class="k">this</span><span class="p">(</span><span class="n">ObservedFeaturesList</span> <span class="n">extObservedList</span><span class="p">)</span>
	<span class="p">{</span>
		<span class="k">super</span><span class="p">();</span>
		
		<span class="k">foreach</span><span class="p">(</span><span class="n">itemKey</span><span class="p">,</span> <span class="n">itemValue</span><span class="p">;</span> <span class="n">extObservedList</span><span class="p">.</span><span class="n">features</span><span class="p">)</span>
		<span class="p">{</span>
			<span class="n">featureItem</span> <span class="p">=</span> <span class="k">new</span> <span class="n">FeatureCheckMenuItem</span><span class="p">(</span><span class="n">extObservedList</span><span class="p">,</span> <span class="n">itemKey</span><span class="p">);</span>
			<span class="n">featureItemArray</span> <span class="p">~=</span> <span class="n">featureItem</span><span class="p">;</span>
			<span class="n">append</span><span class="p">(</span><span class="n">featureItem</span><span class="p">);</span>
		<span class="p">}</span>
		
		<span class="n">exitItem</span> <span class="p">=</span> <span class="k">new</span> <span class="n">ExitItem</span><span class="p">(</span><span class="n">extObservedList</span><span class="p">);</span>
		<span class="n">append</span><span class="p">(</span><span class="n">exitItem</span><span class="p">);</span>
		
	<span class="p">}</span> <span class="c1">// this()</span>

<span class="p">}</span> <span class="c1">// class FileMenu</span>
</code></pre></div></div>

<p>Note that when using an associative array with a <code class="language-plaintext highlighter-rouge">foreach</code> loop, we need to name a pair of iterators, a <code class="language-plaintext highlighter-rouge">key</code> and a <code class="language-plaintext highlighter-rouge">value</code>, as well as the associative array even though we don’t actually use <code class="language-plaintext highlighter-rouge">itemValue</code>. Within the loop, we do the standard stuff:</p>

<ul>
  <li>grab the item’s name from <code class="language-plaintext highlighter-rouge">features</code>,</li>
  <li>create the <code class="language-plaintext highlighter-rouge">CheckMenuItem</code>,</li>
  <li>add it to the local array of <code class="language-plaintext highlighter-rouge">FeatureCheckMenuItem</code>s, and</li>
  <li>append it to the <code class="language-plaintext highlighter-rouge">Menu</code>.</li>
</ul>

<p>Once we’re done with those, it’s back to adding the <code class="language-plaintext highlighter-rouge">exitItem</code> in the usual way.</p>

<p>One last bit to look at…</p>

<h2 id="the-featurecheckmenuitem-class">The FeatureCheckMenuItem Class</h2>

<p>There’s a little more going on here than with other types of <code class="language-plaintext highlighter-rouge">MenuItem</code>. Here’s the code:</p>

<div class="language-d highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="k">class</span> <span class="n">FeatureCheckMenuItem</span> <span class="p">:</span> <span class="n">CheckMenuItem</span>
<span class="p">{</span>
	<span class="nb">string</span> <span class="n">labelText</span><span class="p">;</span>
	<span class="n">ObservedFeaturesList</span> <span class="n">observedList</span><span class="p">;</span>
   
	<span class="k">this</span><span class="p">(</span><span class="n">ObservedFeaturesList</span> <span class="n">extObservedList</span><span class="p">,</span> <span class="nb">string</span> <span class="n">extLabelText</span><span class="p">)</span>
	<span class="p">{</span>
		<span class="n">labelText</span> <span class="p">=</span> <span class="n">extLabelText</span><span class="p">;</span>
		<span class="k">super</span><span class="p">(</span><span class="n">labelText</span><span class="p">);</span>

		<span class="n">observedList</span> <span class="p">=</span> <span class="n">extObservedList</span><span class="p">;</span>
		<span class="n">addOnToggled</span><span class="p">(&amp;</span><span class="n">toggleFeature</span><span class="p">);</span>
		<span class="n">setActive</span><span class="p">(</span><span class="n">observedList</span><span class="p">.</span><span class="n">getFeature</span><span class="p">(</span><span class="n">labelText</span><span class="p">));</span>
		
	<span class="p">}</span> <span class="c1">// this()</span>
	
	
	<span class="kt">void</span> <span class="n">toggleFeature</span><span class="p">(</span><span class="n">CheckMenuItem</span> <span class="n">mi</span><span class="p">)</span>
	<span class="p">{</span>
		<span class="k">if</span><span class="p">(</span><span class="n">getActive</span><span class="p">()</span> <span class="p">==</span> <span class="kc">true</span><span class="p">)</span>
		<span class="p">{</span>
			<span class="n">observedList</span><span class="p">.</span><span class="n">setFeature</span><span class="p">(</span><span class="n">labelText</span><span class="p">,</span> <span class="kc">true</span><span class="p">);</span>
		<span class="p">}</span>
		<span class="k">else</span>
		<span class="p">{</span>
			<span class="n">observedList</span><span class="p">.</span><span class="n">setFeature</span><span class="p">(</span><span class="n">labelText</span><span class="p">,</span> <span class="kc">false</span><span class="p">);</span>
		<span class="p">}</span>
		
	<span class="p">}</span> <span class="c1">// toggleFeature()</span>
	
<span class="p">}</span> <span class="c1">// class FeatureCheckMenuItem</span>
</code></pre></div></div>

<p>Because the individual <code class="language-plaintext highlighter-rouge">CheckMenuItem</code>s differ only in label text, we can get away with this being a generic class and deal with the naming step up in the <code class="language-plaintext highlighter-rouge">FileMenu</code> class we just looked at. The constructor gets access to the <code class="language-plaintext highlighter-rouge">ObservedFeaturesList</code> object like everyone else.</p>

<p>After calling the super-class constructor and setting a couple of local variables, the callback is attached and then we come to:</p>

<div class="language-d highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">setActive</span><span class="p">(</span><span class="n">observedList</span><span class="p">.</span><span class="n">getFeature</span><span class="p">(</span><span class="n">labelText</span><span class="p">));</span>
</code></pre></div></div>

<p>As mentioned above in the section on The <code class="language-plaintext highlighter-rouge">ObservedFeaturesList</code> object, this function defers the decision about the <code class="language-plaintext highlighter-rouge">CheckMenuItem</code>’s state to the observed list object.</p>

<p>Next time, we’ll do pretty much the same thing except with <code class="language-plaintext highlighter-rouge">RadioMenuItem</code>s. However, the mutual-exclusivity of <code class="language-plaintext highlighter-rouge">RadioMenuItem</code>s demands a different approach in a few areas.</p>

<p>Until then, happy coding, happy hunting, happy birthday, or happy New Year, whatever’s your poison.</p>

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